In the prior art bicycle, the treadle is combined with a toe positioning device. The treadle is installed with a front clamper and a rear clamper which provides elastic tightening forces so as to position the bicycle toe positioning device so that the legs of the user can combine with the treadle. When the legs of the user desire to leave from the treadles, the legs rotate to make the bicycle toe positioning device to separate from the front clamper and the rear clampers. Thus the legs can leave from the toe positioning device.
However, in driving the bicycle, it is possible that the leg of the user rotates so that the toe positioning device separates from the treadle. As a result, it is possible that some accident occurs.
Therefore, in one improvement, the elastic units of the front clamper and the rear clamper are arranged with respective screws as adjusters. Rotating the screw will tighten the elastic unit which has a form of a twisting spring. Thus the front clamper and the rear clamper provide more forces to tightly clamp the toe positioning device.
However, increment of the clamping force will make the spring deform. If the elastic unit is over-tight due to the screw force from the screw, it is possible that the spring will fatigue so that the driver cannot concentrate his (or her) attention to drive the bicycle.
Thus it is known that only provide adjusters to the toe positioning device is not enough for resolving the problem of the toe positioning device to separate from the treadle due to a mistake in the operation. Other design is necessary to provide a more safe and concrete structure to the toe positioning device so as to achieve the requirement of safety driving and easy operation in driving a bicycle.